The longterm goals of this project are as follows: 1) To study the cellular processes of synthesis, storage and secretion of growth hormone from the somatotrope and prolactin from the lactotrope. 2) To define the biochemical events associated with alterations in hormone synthesis, storage and secretion (including cyclic nucleotides, prostaglandins, monovalent and divalent cations, release and release inhibiting hormones). 3) To define the physiologic regulators of adenohypophysial hormone production, to study the mechanisms by which they alter hormone production; and hopefully, to gain insight into pathologic regulation of hormone production. The specific aims of this project that have been pursued during the past year are as follows: 1) To define the neurohormonal regulation of somatostatin secretion. We have focussed on serotoninergic regulation during the past grant year. 2) To develop a radioreceptor assay for somatostatin. 3) To define a role for the calcium dependent activator of phosphodiesterase in regulation of adenylate cyclase. 4) To continue the studies of the metabolic and hormonal effects of growth hormone in dwarfed children. 5) Continued clinical studies of hyperprolactinemic subjects. Further definition of the utility of clinical provacative tests (phenothiazines and insulin-induced hypoglycemia) in the evaluation of hyperprolactinemic subjects. 6) Studies of prostaglandin as a tissue hormone regulating cell function.